Commit f8321fa7 authored by Breno Leitao's avatar Breno Leitao Committed by Jakub Kicinski
Browse files

virtio_net: Fix napi_skb_cache_put warning 



After the commit bdacf3e3 ("net: Use nested-BH locking for
napi_alloc_cache.") was merged, the following warning began to appear:

	 WARNING: CPU: 5 PID: 1 at net/core/skbuff.c:1451 napi_skb_cache_put+0x82/0x4b0

	  __warn+0x12f/0x340
	  napi_skb_cache_put+0x82/0x4b0
	  napi_skb_cache_put+0x82/0x4b0
	  report_bug+0x165/0x370
	  handle_bug+0x3d/0x80
	  exc_invalid_op+0x1a/0x50
	  asm_exc_invalid_op+0x1a/0x20
	  __free_old_xmit+0x1c8/0x510
	  napi_skb_cache_put+0x82/0x4b0
	  __free_old_xmit+0x1c8/0x510
	  __free_old_xmit+0x1c8/0x510
	  __pfx___free_old_xmit+0x10/0x10

The issue arises because virtio is assuming it's running in NAPI context
even when it's not, such as in the netpoll case.

To resolve this, modify virtnet_poll_tx() to only set NAPI when budget
is available. Same for virtnet_poll_cleantx(), which always assumed that
it was in a NAPI context.

Fixes: df133f3f ("virtio_net: bulk free tx skbs")
Suggested-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarBreno Leitao <leitao@debian.org>
Reviewed-by: default avatarJakub Kicinski <kuba@kernel.org>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarJason Wang <jasowang@redhat.com>
Reviewed-by: default avatarHeng Qi <hengqi@linux.alibaba.com>
Link: https://patch.msgid.link/20240712115325.54175-1-leitao@debian.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 217b953a

drivers/net/virtio_net.c

+4 −4
Original line number Diff line number Diff line
@@ -2750,7 +2750,7 @@ static int virtnet_receive(struct receive_queue *rq, int budget, 
	return packets;

}



static void virtnet_poll_cleantx(struct receive_queue *rq)

static void virtnet_poll_cleantx(struct receive_queue *rq, int budget)

{

	struct virtnet_info *vi = rq->vq->vdev->priv;

	unsigned int index = vq2rxq(rq->vq);
@@ -2768,7 +2768,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq) 


		do {

			virtqueue_disable_cb(sq->vq);

			free_old_xmit(sq, txq, true);

			free_old_xmit(sq, txq, !!budget);

		} while (unlikely(!virtqueue_enable_cb_delayed(sq->vq)));



		if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) {
@@ -2813,7 +2813,7 @@ static int virtnet_poll(struct napi_struct *napi, int budget) 
	unsigned int xdp_xmit = 0;

	bool napi_complete;



	virtnet_poll_cleantx(rq);

	virtnet_poll_cleantx(rq, budget);



	received = virtnet_receive(rq, budget, &xdp_xmit);

	rq->packets_in_napi += received;
@@ -2935,7 +2935,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) 
	txq = netdev_get_tx_queue(vi->dev, index);

	__netif_tx_lock(txq, raw_smp_processor_id());

	virtqueue_disable_cb(sq->vq);

	free_old_xmit(sq, txq, true);

	free_old_xmit(sq, txq, !!budget);



	if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) {

		if (netif_tx_queue_stopped(txq)) {